Are you aware that the majority of pre-revolution willing immigrants (so not counting slaves) to what eventually became the US came under indentured service? This is basically voluntary time-bound slavery. They, too, had a choice. They, too, had full rights to complain about it afterwards. It was a good thing that that was abolished.

Not everyone coming here is fully aware of the consequences of what they are doing or have been misled. Additionally, humans are allowed to change their minds; and as you get settled in the country you lose that opportunity. Indentured service was orders of magnitudes worse than what H1-B does but there are a lot of similarities in the situations involved and the arguments surrounding them.